This invention relates to a process for measuring the volume of an object, and to an apparatus implementing the process.
A problem shared by many segments of industry and trade is that of assessing the volume of an object. In particular, the supply and shipment of goods demand that the volume of packages be measured in an automated fashion to provide an element of information which is valuable to the conduction of both the storehouse premises and the carrier means.
Storehouse premises and carriers generally handle objects according to their weight, and to one or more of their linear dimensions regarded as most significant. This handling style is, therefore, approximative and surely less than fully satisfactory.
Accordingly, a first aspect of the invention relates to a process for measuring the volume of an object, characterized in that a means of reading an optical code from the object is used.
Optical codes mean here graphical sequences wherein elements of information are recorded in a coded form which can be read by appropriate reading instruments. Examples of optical codes include bar codes, two-dimensional codes, color codes, etc.
In fact, in typical situations where the volume of an object is to be measured (such as package handling through a distribution system or storehouses and the like), an apparatus for reading optical codes would be already provided. The apparatus is inclusive of a set of components (laser units, signal processing units, and processing/storage units) which can be adapted to measure the volume of an object at the expense of a few minor changes and alterations.
Suitably, the optical code reading means comprises a laser scanner, preferably a modulated light scanner, operative to measure the range or distance of a spotted point. A scanner of this type is described, for instance, in U.S. Pat. No. 5,483,051 by this Applicant.
Advantageously, the means of reading may comprise a CCD reader.
The volume may be measured by any of a number of different processes which form the subject matter of specific patent applications filed by the Applicant on this same date. Only the basic features of these processes will be reviewed herein, and for a more detailed explanation, reference can be had to such patent applications.
According to a first of such processes, a volume measurement involves the following steps:
a) placing the object onto a bearing surface;
b) defining a feed direction for the object on the bearing surface;
c) defining a scan plane, intersecting the plane of the bearing surface along a scan base line which lies transverse to the feed direction, with a laser beam from a scanner that overlies the bearing surface being arranged to act in the scan plane;
d) moving the object across the bearing surface along the feed direction, relative to the scan plane, until the scan plane will intersect the object;
e) obtaining the height, above the bearing surface, of n points of measurement contained in a top face of the object and the scan plane;
f) defining a stipulated height as a function of the measured heights of two successive points of measurement;
g) obtaining the plan position on the bearing surface of the n points of measurement;
h) defining a stipulated base as a function of the plan positions on the bearing surface of each pair of adjacent points of measurement;
i) computing a stipulated area element, vertical to the bearing surface, for each pair of adjacent points of measurement, as by multiplying the stipulated base by the stipulated height;
j) computing a stipulated area as the combined sum of the stipulated area elements computed;
k) moving the object relative to the scan plane a predetermined feed distance along a feed direction across the bearing surface;
l) defining a stipulated thickness as a function of the feed distance;
m) computing a volume element by multiplying the stipulated area by the stipulated thickness;
n) repeating steps e) to m) above until the entire object is scanned;
o) computing the object volume as the combined sum of all the volume elements.
The term top face is here a generic one, it encompassing any surface seen by the laser scanner placed above the bearing surface. In particular, even a sloping side surface may be taken to be the top face, whose slope is an upward taper angle of the object as referred to its rest position on the bearing surface.
The movement of step d) above should be understood as a relative movement. Thus, it may either be a movement of the object relative to a fixed scan plane, or a movement of the scan plane relative to an object held stationary, or both.
According to a second of such processes, the volume measurement involves the following steps:
placing the object onto a bearing surface;
defining a feed direction for the object on the bearing surface;
defining a scan plane, intersecting the plane of the bearing surface along a scan base line which lies transverse to the feed direction, with a laser beam from a scanner that overlies the bearing surface being arranged to act in the scan plane;
defining a fixed Cartesian reference system having a longitudinal axis (y) along the feed direction, a transverse axis (x) orthogonal to the longitudinal axis (y), and a vertical axis (z) orthogonal to the plane of the bearing surface;
moving the object across the bearing- surface, along the feed direction, relative to the scan plane until the scan plane will intersect the object;
effecting a scan sweep across the object in the scan plane by means of the scanner;
reckoning and storing a set of triads of coordinates (x, y, z) of n points of measurement of the object swept by the laser beam in the scan plane;
moving the object relative to the scan plane through a feed distance in the feed direction equal to a predetermined longitudinal resolution (L);
repeating the three last-mentioned steps until the entire object is scanned;
establishing a set of standard values (xxe2x80x3) for the transverse coordinate separated by a value equal to a predetermined transverse resolution (T);
constructing, for each scan sweep, a set of equivalent triads (xxe2x80x3, yxe2x80x3, zxe2x80x3) representing equivalent points, wherein the values of the transverse coordinate (xxe2x80x3) are equal to the values of the standard set, and the values of the longitudinal coordinate (yxe2x80x3) and the vertical coordinate (zxe2x80x3) are respectively functions of the values of the reckoned longitudinal and vertical coordinates (y, z);
computing the volume included between the bearing surface (x, y) and the surface defined by those points which have equivalent coordinates (xxe2x80x3, yxe2x80x3, zxe2x80x3).
Here again, the movement of the object across the bearing surface in the feed direction, with respect to the scan plane, should be understood as a relative movement.
According to a third of such processes, the volume measurement involves the following steps:
placing the object onto a bearing surface;
defining a feed direction for the object on the bearing surface;
defining a scan plane, intersecting the plane of the bearing surface along a scan base line which lies transverse to the feed direction, with at least one laser beam from the scanner that overlies the bearing surface being arranged to act in the scan plane;
defining a read plane intersecting the plane of the bearing surface along a read base line which lies transverse to the feed direction, light beams being active in the read plane which are picked up by the CCD reader located above the bearing surface;
moving the object across the bearing surface, along the feed direction, relative to the scan and read planes such that the object will cross these planes;
effecting a series of scan sweeps across the object in the scan plane with the laser beam, such that at each scan sweep, the positions of n points of measurement defining the object outline as spotted by the laser beam are reckoned;
effecting a corresponding series of readings of the object by means of the CCD reader to reckon, at each reading, the maximum width of the object outline as spotted by the CCD reader, each reading being offset in time with respect to the corresponding laser scan sweep by a necessary time period to allow the reading to be effected at the same location on the object where the scan sweep was effected;
processing the information from each scan sweep along with the information from the corresponding reading to define a set of stipulated outlines of the object;
computing the area of each stipulated outline;
computing a feed distance travelled by the object between two successive scan sweeps or between two successive readings;
computing, for each stipulated outline, an elementary volume as the product of the area of the stipulated outline by the feed distance;
computing the volume of the object as the combined sum of the elementary volumes.
Also in this third case, the movement of the object across the bearing surface in the feed direction, with respect to the scan plane, should be understood as a relative movement.
A second aspect of this invention is related to an optical apparatus for acquiring information about an object, which apparatus includes a means of reading an optical code associated with the object, and is characterized in that it includes a means of measuring the volume of the object.
This apparatus can implement the process outlined hereinabove.
Suitably, this apparatus includes at least one laser scanner which is part of both the optical code reading means and the volume measuring means; preferably, the laser scanner is a modulated light scanner adapted for measuring the range or distance of a spotted point.
Advantageously, the apparatus may additionally include a CCD reader.
Advantageously, the apparatus comprises:
a laser unit including a laser light source and a means of controlling and aiming it;
an analog signal processing unit receiving signals from the laser unit;
an A/D converter receiving, from the analog processing unit, signals related to the distance of the points being spotted by the laser;
a decoder unit receiving, from the analog processing unit, signals related to the optical code;
a processing/storage unit receiving signals from the A/D converter and the decoder unit.
In a first preferred embodiment:
the means of reading the optical code and means of measuring the volume share the laser unit, processing unit, and processing/storage unit;
the means of reading the optical code further includes the decoder unit;
the means of measuring the volume further includes the A/D converter.
It can be appreciated that in this embodiment of the invention, the volume measurement could merely involve the addition of an A/D converter to an apparatus for reading an optical code.
In a second preferred embodiment:
the means of reading the optical code and means of measuring the volume share the processing/storage unit;
the means of reading the optical code further includes a first laser unit, first processing unit, and the decoder unit;
the means of measuring the volume further includes a second laser unit, second processing unit, and the A/D converter.
Even in this, more complicated embodiment, the volume is measured by the same processing/storage unit as is provided for reading the optical code.
The layout of the apparatus components may be any one, for example arranged within the same scan/processing unit.
Advantageously, in a first preferred embodiment:
the processing/storage unit, first laser unit, first processing unit, decoder unit, and A/D converter are all laid within a scan/processing unit;
the second laser unit and second processing unit are laid within a scan unit.
Advantageously, in a second preferred embodiment:
the processing/storage unit, second laser unit, second processing unit, decoder unit, and A/D converter are all laid within a scan/processing unit;
the first laser unit and first processing unit are laid within a scan unit.
Advantageously, in a third preferred embodiment:
the processing/storage unit, decoder unit, and A/D converter are all laid within a processing unit;
the first laser unit and first processing unit are laid within a first scan unit;
the second laser unit and second processing unit are laid within a second scan unit.
Scan-only units take up less space than processing units or scan/processing units. Accordingly, the arrangements of the apparatus members which include a scan-only unit are to be preferred where space requirements are critical in the object scan zone.
Advantageously, the laser unit may comprise two laser emitters and a single moving-mirror deflector, the deflector having two discrete sets of mirror surfaces at an angle to one another for the emitter pair. This dual scanner configuration allows the scanning to be performed in different planes for code reading and volume measurements, while using a single moving-mirror deflector.